The present invention relates to a rotary machine of a motor or a generator comprising a rotor and a stator and more particularly to a coil to be inserted into the slot of the stator and a manufacturing method of the coil.
A stator of a motor such as an induction motor or synchronous motor which is a rotary machine comprises a core and coils and as shown in FIG. 2 and the coils are arranged in many slots provided in the core three-dimensionally so as to be overlaid each other. The inserter system for inserting coils for producing the stator into the slots is indicated in, for example, Japanese Patent Application Laid-Open No. 53-100402. In this inserter system, a method for setting a coil 31 wound in the predetermined shape beforehand in a coil guide 11 called a blade as shown in FIGS. 3a-3c, setting a core 2 in the state that a slot insulating material is inserted, pushing up a push-in jig 14 called a stripper and a wedge pusher 12 using hydraulic pressure, and inserting the coil 31 and a wedge 13 into the slot at the same time is used. However, the coil 31 enters inside the slots one by one as it moves in the longitudinal direction of the core, so that an extra length is necessary in the longitudinal direction of the coil itself and it causes an extra length in the end portion of the coil. Namely, since the inserter system inserts the coil by adjusting the shape thereof, there are problems imposed that the winding occupation rate in each slot of the core (a ratio of the cross-sectional area of the magnet wire including the film to the effective area of each slot in which the insulating material is subtracted) cannot be increased and some extra length is necessary in the conductor portion protruded outside the core, that is, in the end coil portion. On the other hand, in the inserter system, in is consideration of the insertion resistance when the coil 1 wound round the blade 11 is pushed up by the stripper 14 and damage to the coil, the fact is that it is necessary to set the winding occupation rate to about 60 to 70% and the end coil length to about 1/3 to 1/2 of the overall length of the conductor.
In a comparatively large motor, as a manufacturing method for increasing the winding occupation rate, a method for inserting a wound coil 41 directly into a core 2 having an open slot 3 is known as shown in FIG. 4. In this method, it is possible to increase the winding occupation rate in the slot 3. However, to realize the stator arranged as shown in FIG. 2, a rather long extra length is necessary so as to avoid mutual interference with the end coils.
The end coil portion of each coil of the stator exists only for the role for connecting the conductors entering the slots to each other but is not a portion for generating a magnetic field and allowing the motor to generate rotational torque. Therefore, the current flowing through this end coil portion is a useless current in a sense and a part of the copper loss for reducing the efficiency of the motor.
In every prior art mentioned above, there is a problem imposed that a long extra length is necessary in the end coil portion when a coil is inserted into each slot portion of the stator and as a result, the copper loss of the coil increases and the efficiency of the motor decreases.